SM 25x275 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense strength, neodymium magnets offer the following advantages:

• Their power remains stable, and after around 10 years, it drops only by ~1% (according to research),
• They show superior resistance to demagnetization from outside magnetic sources,
• By applying a shiny layer of gold, the element gains a clean look,
• The outer field strength of the magnet shows remarkable magnetic properties,
• With the right combination of magnetic alloys, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the design),
• The ability for precise shaping as well as adjustment to individual needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Key role in advanced technical fields – they serve a purpose in data storage devices, rotating machines, clinical machines or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in tiny dimensions, which makes them useful in small systems

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to external force, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and additionally enhances its overall robustness,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to moisture can rust. Therefore, for outdoor applications, we recommend waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Safety concern from tiny pieces may arise, when consumed by mistake, which is notable in the health of young users. Furthermore, tiny components from these products might complicate medical imaging once in the system,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what it depends on?

The given lifting capacity of the magnet represents the maximum lifting force, calculated in a perfect environment, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• at room temperature

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is affected by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Lifting capacity was measured using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, however under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.